Apparatus and method for detecting a change in output voltage of an isolated power converter

A method of controlling a power converter, comprising:

• switching a power switch to control a transfer of energy from an input of the power converter to an output of the power converter;
• generating a feedback signal representative of the output of the power converter;
• capturing a first peak voltage representative of a second peak of a ringing voltage of the feedback signal at a first time in the feedback signal;
• capturing a second peak voltage representative of the second peak of the ringing voltage of the feedback signal at a second time in the feedback signal;
• and
• varying the transfer of energy from the input of the power converter to the output of the power converter in response to the first and second peak voltages.

A power converter, comprising:

• an energy transfer element coupled between an input of the power converter and an output of the power converter;
• a power switch coupled to the energy transfer element and the input of the power converter;
• a controller including a drive circuit to generate a switching signal coupled to be received by the power switch to control a transfer of energy from the input of the power converter to the output of the power converter;
• and
• an output voltage sensor included in the controller and coupled to the drive circuit, the output voltage sensor coupled to receive a feedback signal representative of the output of the power converter, the output voltage sensor including first and second pulse sampler circuits, the first pulse sampler circuit coupled to capture a first peak voltage representative of a second peak of a ringing voltage of the feedback signal at a first time in the feedback signal, the second pulse sampler circuit coupled to capture a second peak voltage representative of the second peak of the ringing voltage of the feedback signal at a second time in the feedback signal, the output voltage sensor coupled to output a change signal to the drive circuit in response to the first and second peak voltages.